Satiation devices and methods

ABSTRACT

A device for inducing weight loss in a patient includes a tubular prosthesis self-expandable from a collapsed position in which the prosthesis has a first diameter to an expanded position in which the prosthesis has a second, larger, diameter. In a method for inducing weight loss, the prosthesis is placed in the collapsed position and inserted into a stomach of a patient. The prosthesis is allowed to self-expand from the collapsed position to the expanded position and into contact with the walls of the stomach, where it induces feelings of satiety and/or inhibits modulation of satiety-controlling factors such as Ghrelin.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/538,741, filed Aug. 10, 2009, now pending, which is acontinuation of U.S. patent application Ser. No. 10/457,144, filed Jun.9, 2003, now abandoned, which is a divisional of U.S. patent applicationSer. No. 09/940,110, filed Aug. 27, 2001, now U.S. Pat. No. 6,675,809.

FIELD OF THE INVENTION

The present invention relates generally to the field of devices andmethods for achieving weight loss in humans, and, specifically to theuse of devices implantable within the human stomach for controllingfeelings of hunger.

BACKGROUND OF THE INVENTION

Various medical approaches are used for controlling obesity. Theseapproaches include diet, medication, and surgical procedures. One of themore successful surgical procedures is the vertical banded gastroplexyor the proximal gastric pouch with a Roux-en-Y anastomosis. However,known complications are present with each of these procedures and moresuccessful options are desired.

Other alternatives include implantation of gastric balloons that preventovereating by occupying volume within the stomach. Unfortunately,gastric balloons can migrate down the GI tract, causing obstruction andthus necessitating removal.

It is therefore desirable to provide a successful and minimally-invasivealternative to existing approaches for controlling obesity.

SUMMARY OF THE INVENTION

A satiation device utilizing principles of the present inventionincludes a tube having a collapsed position proportioned to permitintroduction of the tube into a portion of the stomach. Once positionedwithin the body, the tube self-expands into contact with the interior ofthe stomach. During use, food ingested into the stomach passes throughthe tube. In an alternate embodiment, the tube may be formed of amaterial that prevents food within the tube from contacting thesurrounding walls of the stomach. In one embodiment, the tube may bepositionable within the antrum of the stomach. In other alternativeembodiments, the device may include a fundal basket which may or may notbe attached to a proximal end of an antral tube, and/or a bowel tubewhich may or may not be attached to a distal end of an antral tube.

In other alternative embodiments, a small pouch is attached to a cagestructure such as a fundal basket and positioned at the proximal end ofthe stomach. In other alternative embodiments, this pouch may heprovided without a cage structure and is independently secured againstthe proximal stomach wall by endoscopy guided sutures or other means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a human stomach and a portion ofthe small intestine.

FIG. 2 is a plan view of a satiation device utilizing principles of thepresent invention.

FIG. 3 is a plan view of a satiation device similar to that of FIG. 2,but including a drug delivery reservoir.

FIG. 4A is a schematic illustration of a stomach, pylorus, and bowel,showing introduction of the device of FIG. 2 or 3 into the antrum.

FIG. 4B is a schematic illustration similar to FIG. 4A, showing thedevice in position.

FIG. 4C is a schematic illustration similar to FIG. 4B, showingwithdrawal of the device into a sheath for subsequent removal from thebody.

FIG. 5 is a schematic illustration similar to the illustration of FIG.4B, showing the position of an alternative device having an antral tubeand a bowel tube.

FIG. 6 is a schematic illustration similar to the illustration of FIG.4B, showing the position of an alternative device having an antral tubethat does not cross the pyloric sphincter.

FIG. 7 is a plan view of an antral tube similar to the antral tube ofFIG. 6, with retaining structures formed into the external surface.

FIG. 8 is a plan view of an antral tube similar to the antral tube ofFIG. 6, with retaining structures formed at the proximal and distalends.

FIGS. 9A and 9B are plan views of antral tubes similar to the antraltube of FIG. 6, with variations of retaining ridges formed on theirexternal surfaces.

FIGS. 10A-10C are perspective views of satiation devices having antraltubes and fundal baskets.

FIGS. 10D-10F are partial side elevation views of satiation deviceshaving antral tubes and bowel tubes. Each figure illustrates a portionof the antral tube and a portion of the bowel tube.

FIG. 11 is a plan view of a satiation device having an antral tube,fundal basket, and bowel tube.

FIG. 12A is a plan view schematically illustrating insertion of a devicesuch as the devices of FIGS. 10A-10C into the body.

FIG. 12B is a plan view schematically illustrating removal of the devicesuch as the devices of FIGS. 10A-10C from the body.

FIG. 13 schematically illustrates an alternative embodiment of asatiation device positioned within a human stomach.

FIG. 14 is a side elevation view of a satiation device utilizing a coilconfiguration.

FIG. 15 schematically illustrates the satiation device of FIG. 15positioned within a human stomach.

FIGS. 16A and 16B are end views of a tube for a satiation device, suchas a fundal basket, antral tube, or bowel tube, illustrating tab membersthat may be utilized to facilitate tube removal.

FIG. 17A schematically illustrates in vivo positioning of an alternativesatiation device utilizing a standalone stomach pouch.

FIG. 17B is a schematic illustration similar to FIG. 17A, but furtherillustrating a cage in combination with the stomach pouch.

FIG. 17C is a schematic illustration similar to FIG. 17B, but furtherillustrating an alignment extension in combination with the stomachpouch and cage.

FIG. 18 is a perspective view of a stomach pouch of a type that may beutilized as shown in FIGS. 17A-17C.

FIG. 19A is a perspective view of an alternative stomach pouch of a typethat may be utilized as shown in FIGS. 17A-17C.

FIG. 19B is a cross-sectional side view of the stomach pouch of FIG.19A.

FIG. 20 illustrates in vivo positioning of an alternative satiationdevice utilizing a duodenal absorption barrier prosthesis.

DETAILED DESCRIPTION

An anatomical view of a human stomach S and associated features is shownin FIG. 1. Stomach S includes a fundus F at its proximal end and anantrum A at its distal end. Antrum A feeds into the pylorus P whichattaches to the duodenum D, the proximal region of the small intestine.Within the pylorus P is a sphincter that prevents backflow of food fromthe duodenum D into the stomach. The middle region of thesmall-intestine, positioned distally of the duodenum D, is the jejunumJ.

Various embodiments of satiation devices are described herein. Many ofthese devices include an antral tube positionable within the antrum A,and may optionally include a fundal tube connected to the proximal endof the antral tube for placement in the fundus F, and/or a bowel tubeconnected to the distal end of the antral tube for placement in theduodenum D.

The device may be modular in that the various components may be providedseparate from one another. In such a modular system, the separateimplanted components may be attached to one another within the bodyduring implantation, or certain ones of them may remain unattached toone another even after implantation. Alternatively, the physician mayassemble the components to one another just prior to implantation.Modular components are desirable in that they permit the physician toselect sizes for each component that are appropriate for the patient. Asanother alternative, the device may be a unitary device in the sensethat the components (e.g. the antral tube, bowel tube and/or fundalbasket) are not separately provided but instead form a single-unitimplant.

FIG. 2 shows a first embodiment of a satiation device 100 utilizingprinciples of the present invention. Satiation device 100 includes anelongate tubular body 10 having a proximal section 12 and a distalsection 14. Proximal section 12 includes a reduced diameter neck 16.Distal section 14 preferably has an hourglass profile including a pairof broadened sections 18 and a waisted section 20 between the broadened.sections.

Tubular body 10 is proportioned to be at least partially positionedwithin the antrum of the stomach such that food moving into the antrumpasses through the hollow interior of the tubular body. The tubular body10 (which will also be referred to as the antral tube) may be made ofshape memory materials such as nitinol or other shape memory alloys, orshape memory polymers, and is preferably made of a soft mesh or otherframework formed of nitinol or stainless steel wires in combination witha polymeric barrier that prevents ingested food passing through theantral tube 10 from contacting the walls of the antrum. Thus, thepolymeric barrier may be a skin formed on the exterior or interior ofthe mesh, or the mesh may be encapsulated in polymeric material or thepolymer may be disposed in the interstices of the mesh. By preventingfood from contacting the antrum walls as it passes from mid-stomach tothe pylorus, the device prevents modulation of Ghrelin or other satietycontrolling factors.

As shown in FIG. 3, the device 100 may optionally include one or morepharmaceutical delivery reservoirs 22, which are filled with substancesknown to inhibit release of Ghrelin or other hormones associated withfeelings of satiety. Such substances may be chemical or pharmaceuticalsubstances, therapeutic molecules or cells, or genetic material. Eachsuch reservoir 22 may comprise a fluid pocket formed between a firstlayer of fluid impermeable polymeric material and a second layer ofsemi-permeable membrane that allows the substances to pass from thereservoirs into the surrounding tissue. Alternatively, the polymericmaterial used to form the tube may be impregnated with substances usefulfor maintaining low Ghrelin levels.

The reservoir or material containing the inhibitive substances may be ina portion of the device that lies within the antrum and/or in a portionthat lies within the duodenum, particularly the segment of the duodenumthat is proximal of the ampulla of vader, as it is believed thatreceptors for such substances are present in these areas.

During implantation, the antral tube 10 is passed into the patientblindly, under radiologic guidance, or under endoscopic guidance. Priorto implantation. the antral tube 10 is preferably packaged in a tubularsheath 26 (see FIG. 4A) by compressing the antral tube 10 about itslongitudinal axis and inserting it into tubular sheath 26.

The sheath 26, with the antral tube 10 packaged inside, is passed intothe stomach via the patient's mouth and positioned within the antrum asshown in FIG. 4A. The antral tube 10 is then pushed out the distal endof the sheath 26 using a pushing device 28 inserted into the proximalend of the sheath. The mesh forming the antral tube is preferablyconstructed so as to be self-expanding, such that the tube 10 springsradially open into an expanded condition upon its ejection from thesheath 26. When in its expanded condition, the antral tube exertspressure against the interior surfaces against which it is in contact,so as to create the feeling of satiety and to inhibit Ghrelin release.The radial pressure of the device against the walls also secures thedevice against the walls of the antrum and prevents it from movingthrough the pylorus, even in the presence of peristalsis. In analternative embodiment, the antral section is covered, such as by apolymeric material, shielding the stomach contents from the antrum. Thismay suppress chemical mediators of the sensation of hunger, such asGhrelin production.

The hour-glass shape of the distal portion 14 is configured such thatwhen the device is implanted, the waist section 20 becomes seated at thepyloric sphincter as shown in FIG. 4B. This helps to prevent migrationof the device within the stomach, yet because of the self-expandingnature will avoid obstruction of the pylorus. It may be additionallydesirable to provide the antral tube to include a valve (not shown)within the waist section 20, so as to prevent reflux of bile from theduodenum into the antrum.

Referring to FIG. 4C, removal of the device is carried out by insertingsheath 26 into the stomach, and by extending a grasping instrument suchas snare 30 through the sheath. Snare 30 is closed around the neck 16 ofthe tube 10 and withdrawn, causing the tube 10 to collapse and be drawninto the sheath 26. Once the tube 10 is stored within the sheath, thesheath is withdrawn from the patient.

It will be appreciated that various other mechanisms may be used tofacilitate collapse of the tube for removal. For example, FIGS. 16A and16B show end views of the proximal portion of an alternative antral tube11 which is provided to include one or more radially extending tabs 13.Tabs 13 are preferably rounded and smooth to minimize interference withflow through the tube 11. When the satiation device is to be removed,tabs 13 are drawn inwardly using endoscopic instruments, causing thetube to collapse inwardly.

Referring to FIG. 5, an alternate embodiment of satiation device 110includes an antral tube 10 a similar to that of the previousembodiments, but additionally includes a small diameter bowel tube 32 atits distal end. The bowel tube 32 is preferably formed of a combinationof mesh and polymer as described in connection with antral tube 10 ofFIG. 2. It simulates a Roux en Y, or gastric bypass, procedure bykeeping food away from the proximal portion of the small bowel (i.e.away from the duodenum or the jejunum and duodenum, the portions of thesmall intestine at which most carbohydrates and proteins are absorbed bythe body). This in turn prevents absorption of food by the proximalportion of the small bowel, and thus reduces the total amount of foodabsorbed by the body.

The bowel tube 32 is smaller in diameter than the antral tube 10 a, andis of a diameter that will allow it to press gently against the walls ofthe small bowel. It must also be sufficiently flexible to passposteriorly and distally into the second portion of the duodenum withoutdamaging the mucosa. This may be facilitated by the use of a guidewirethat is first introduced with an endoscope.

The bowel tube 32 may be a soft wire mesh (formed, for example, of shapememory alloys, nitinol. stainless steel alloys, stainless steel orpolymers including shape memory polymers) covered with a polymer toprevent food and digestive juices from contacting the mucosa of theduodenum. Tube 32 may be provided to have a valve 34 at its distal end,which functions to prevent reflux of intestinal contents. The bowel tubeincludes an opening 33 to ensure that the ampulla of vader is notobstructed.

Delivery of the device 110 into, and its removal from the stomach may beperformed under radiological or endoscopic guidance as described withrespect to the prior embodiments. A conventional guide wire may also beused to facilitate positioning of the bowel tube 32. If a guide wire isused, it is first placed into the duodenum using endoscopy or radiologyto guide the wire placement. The bowel tube 32 and antral tube 10 a arethen placed over the wire and guided over the wire into the duodenum orjejunum to the desired location. Next, the guide wire is removed. Thesmall bowel tube position is maintained by bearing against the proximalend of the antral tube using a pushing instrument (such as the pusher 28shown in FIG. 4A), while the covering sheath is withdrawn. As they arereleased from the sheath, the small bowel tube and the antral tubedeploy and expand into contact with the antrum walls.

In a modular version of the device 110, the antral tube 10 a and boweltube 32 may be provided separately. Components of a modular system maybe attached to one another pre-operatively or after each component hasbeen positioned within the body.

An alternative form of a satiation device 120 may be configured, asshown in FIG. 6, to have an antral tube 10 b that is positioned onlywithin the antrum and that does not cross the pyloric sphincter. As withthe prior embodiments, the satiation device 120 is preferablyself-expanding and may be formed of a soft nitinol, shape memorypolymer, or stainless steel mesh, preferably in combination with apolymer. Outward radial pressure between the antral tube and the stomachwalls prevent the tube from moving distally through the pylorus, even inthe presence of peristalsis. Additional mechanisms may be provided toprevent movement of the tube towards the fundus and/or pylorus. Forexample, soft and directional “fish scale” type structures 36 may beformed on the mesh or polymer on the exterior surface of the antral tube10 b as shown in FIG. 7. The figure shows the scales oriented to preventmovement of the device towards the pylorus, but it should be appreciatedthat movement towards the fundus may be prevented by orienting thescales in the opposite direction.

A plurality of hooks 38 may be formed on the proximal and/or distal endsof the antral tube 10 b, as shown in FIG. 8. These hooks gently attachto the mucosa of the antrum and prevent movement in the proximal and/ordistal direction. Such hooks should be sufficiently small as to notpenetrate the submucosa or muscularis.

FIGS. 9A and 9B illustrate the use of ridges formed on the exterior ofthe antral tube for preventing migration of the tube. The ridges may beformed in a variety of configurations, such as the helical ridges 40shown on the FIG. 9A embodiment or the rings 42 shown in the FIG. 9Bembodiment. These same mechanisms for preventing movement may be appliedto the bowel tube as well, as described with respect to FIGS. 10D-10F.

A basket structure may extend from the proximal end of the antral tubefor positioning in the fundus. Referring to FIGS. 10A-10C, a fundalbasket 44 a, 44 b, 44 c may be formed of a mesh provided with largeopenings sized to permit food to readily flow through the fundal basketinto the antral tube. Unlike the mesh of the antral tube, the mesh ofthe fundal basket is preferably not covered with a polymeric skin orcoating. The fundal basket is mechanically connected to the antral tube,such as by spring members 46 a (FIG. 10A), elongate struts 46 b (FIG.10B), mesh 46 c (FIG. 10C) or equivalent structural components. Theproximal end of the fundal basket rests against the walls of the fundusof the stomach and thereby functions to prevent migration of the devicewithin the stomach. An embodiment utilizing an antral tube and fundalbasket may be provided in a modular form—in which the antral and fundalcomponents are separate from one another and then attached to oneanother pre-operatively or following implantation in the body.Alternatively, the antral tube and fundal basket may comprise a unitarydevice.

Similar attachment mechanisms may be used to attach a bowel tube to anantral tube in embodiments having these components, regardless ofwhether a fundal basket is used. For example, the bowel section 132 band antral section 110 b may be connected with one or more longitudinalstruts, as shown in FIGS. 10E and 10F. An alternative embodiment may beprovided without an attachment strut, in which case bowel tube 132 a maybe placed separately from antral tube 110 a, and it may include a necksection 133 (or tabs such as tabs 13 of FIGS. 16A/16B) at its proximaledge to allow recovery with an endoscopically controlled snare. See FIG.10D. As discussed previously, a device of this type may be provided as amodular or unitary device.

Referring to FIG. 11, embodiments having an antral tube 10 b and afundal basket 44 may further include a bowel tube 32 attached to theantral tube. As discussed previously with respect to FIG. 5, the boweltube 32 functions to keep food away from the proximal small bowel. Thebowel tube 32 may have properties similar to those described withrespect to the embodiment of FIG. 5.

As with the previous embodiment, the embodiments of FIGS. 10A-10F and 11are preferably inserted into the stomach in a collapsed condition, suchas within a sheath 26 as shown in FIG. 12A. In the case of the FIG.10A-10C embodiments which include antral and fundal tubes only, thedistal tip of the antral tube is placed at the pylorus (or across thepylorus as with the FIG. 2 embodiment) and the sheath is withdrawn. Asthey are released, the antral and fundal units self-expand and mayshorten slightly.

If a small bowel tube is to be included, as in FIGS. 10D-10F, the tubecan be placed under radiological guidance or endoscopic guidance or overa guide wire as described above with respect to FIG. 5. As discussed,the antral tube, fundal basket and bowel tube may form parts of aunitary device, or they may be separately provided as modularcomponents. In a modular device, each of the three components may beseparately provided and then attached to one another prior toimplantation or after the components have been positioned within thebody. In another form of modular device, some but not all of thecomponents (e.g. the fundal basket and antral tube, or the antral tubeand bowel tube) may comprise a unitary device, and an additional modularcomponent may be provided for subsequent attachment to the unitarydevice either before or after implantation.

Referring to FIG. 12B, removing the device, whether it includes only anantral tube, fundal and antral tubes, or fundal, antral and small boweltube, is accomplished by extending a sheath 26 into the stomach,extending a grasping instrument through the sheath, grasping theproximal end of the device and pulling the tube into the sheath causingit to collapse. If a wire snare loop is to be used as the graspinginstrument, the snare is placed around a neck (such as neck 16 shown inFIG. 2 or a similar neck 17 at the proximal end of the fundal basket asshown in FIG. 12B) to grasp the device. Engagement with the snare loopwould assist in collapsing the tube as the snare is tightened around theneck and withdrawn into the sheath 26. Alternatively, as described withrespect to FIGS. 16A and 16B, the proximal end of the tube may includetabs 13 that are pulled radially inwardly using an endoscopic instrumentto facilitate collapse of the device.

Another alternative satiation device 130 is shown in FIG. 13. As withthe prior devices, device 130 includes an antral tube 10 c positionablewithin the antrum to minimize direct contact between food entering theantrum and the walls of the antrum. The antral tube 10 c may be formedof a combination of soft polymeric material as well as reinforcingmembers formed of nitinol, stainless steel, and/or polymer. In theembodiment shown in FIG. 13, device 130 is formed of a polymeric sleeve48 with nitinol struts 50 embedded in the sleeve material. Stainlesssteel or polymeric reinforcing bands 52 extend longitudinally along theinterior walls of the tubular member. Inflatable reservoirs 54 formed ofa soft elastic polymer are positioned on the exterior of the tubularsleeve 48. A fill tube 56 is fluidly coupled to the reservoirs. Afterthe device is positioned within the antrum, reservoirs 54 are filledwith saline to expand the sleeve 48 into contact with the antrum walls,so as to hold the device in place within the antrum. Fill tube 56 maydetach from the reservoir following inflation using the saline. Toprevent saline leakage, a one-way valve (not shown) may be locatedwithin the reservoir at the point of attachment of the fill tube.

Another alternative embodiment of a satiation device 200 is shown inFIGS. 14 and 15. The device may be formed of a wire member coiled tocreate a stent-like device. The coil may be contoured to match thecontours of interior lumen wall, such as by forming the coil of a shapememory material such as nitinol or polymers, and shape setting thematerial to the desired shape. Device 200 has a proximal portion 202positionable in the antrum, and a distal portion 204 that may bepositioned in the duodenum bulb or further within the small intestine.The pitch of the coil is selected to give the device 200 a desiredstrength and flexibility.

A straight portion 206 connects the proximal and distal portions 202,204. Straight portion 206 is positionable within the pyloric sphincter.Under normal conditions, the pyloric sphincter remains closed. until thestomach is ready to evacuate its contents into the duodenum. Straightportion 206 is beneficial in that it provides structure connectingproximal and distal portions 202, 204 while allowing the pyloricsphincter to correctly perform its normal function.

Although a preferred material for the device 200 is wire, it should benoted that a variety of alternative materials may be used for thispurpose. For example, device 200 may be formed of ribbons of material,or it may be formed from a metallic sheet, or its pattern may be cutfrom tubing.

Yet another embodiment of a satiation device 300 is illustrated in FIG.17A. Device 300 includes a tubular pouch 302 that is positioned in theproximal region of the stomach. Pouch 302 includes a proximal end thatis preferably positioned to be slightly proximal of the gastroesophagealjunction as shown. The walls of the pouch preferably taper inwardly fromthe proximal end towards the distal end. A proximal opening 304 of, forexample, approximately 25 to 50 mm in diameter is located at theproximal end and a distal opening 308 having a diameter of approximately6-12 mm is formed at the distal end. The proximal opening 304 ispreferably placed into alignment with the esophagus, and the distalopening 308 opens into the interior of the stomach.

Because of its small volume (which may be on the order of approximately30 cc-50 cc in volume), the pouch functions to limit the amount of foodthat can be consumed at one time. Food ingested by the patient remainsin the pouch until digestive enzymes have broken it down sufficientlyfor it to pass through the distal opening 308.

The pouch is preferably self-expanding and may take a variety of forms.For example, referring to FIG. 18 it may be formed of struts 310 or amesh formed of nitinol, stainless steel, polymer (including shape memorypolymer). A ring 312 is attached to the struts/mesh at the proximal endof the device, and also may be formed of nitinol, stainless steel,polymer (including shape memory polymer). The exterior or interior ofthe pouch covered with a material 313 will prevent passage of foodthrough the sides of the pouch. One example of such a material is apolyester material such as the polyester sold by the DuPont Companyunder the trademark Dacron.

FIGS. 19A and 19B show another example of a pouch 302 a. Pouch 302 a isformed of a shape memory coil that has been heat set to a funnel shape.Dacron polyester or other material 313 a (FIG. 19B) may optionally coverthe interior or exterior walls of the coil, although the coil may itselfbe sufficiently small as to prevent migration of food to the surroundingstomach walls. The material 313 a may be pinched between proximal-mostcoil 312 a and its adjacent coil as shown in FIG. 19B. so as to hold itin place.

The pouches 302, 302 a may be provided with a proximal-to-distaldimension that is fairly long (e.g. on the order of approximately2.5-5.0 cm) and that thus gives the pouch a funnel shape as shown inFIGS. 18 and 19A. However, a variety of alternative shapes may be usedfor the pouch. For example, the pouch may have a much shorterproximal-to-distal dimension and thus take the shape of a shallow saucerwith a small hole on its bottom surface.

The stomach pouch may be used alone or in combination with othercomponents. If used without additional components, the proximal end ofthe pouch (e.g. ring 312 of pouch 302 or ring 312 a of pouch 302 a) mayserve as a sewing ring that is attached by sutures to the interiorstomach walls. The suture may pass through the material 313, 313 a (seeFIG. 19B) to strengthen the connection between the stomach wall and thedevice. Alternatively, the pouch may be used as a standalone devicewithout sutures—in which case it may be held in place by the radialexpansion forces of the struts, mesh or coils.

The stomach pouch may alternatively be one portion of a larger satiationdevice. For example, referring to FIG. 17B, the proximal portion of thepouch (such as ring 312 of the pouch of FIG. 18 or the upper coil 312 aof the pouch of FIG. 19A) may be connected to the proximal end of alarger cage structure 314. Cage 314 extends from the esophagus to theproximal portion of the antrum, and may be similar to the fundal basketsdescribed above. It may be a large stent-like structure preferablyformed of self-expanding material, such as stainless steel or a shapememory material such as nitinol or polymer. Cage 314 functions primarilyto distend the stomach to create a feeling of satiety. As shown, thepouch 300 is suspended into the interior of cage 314.

Additionally, the pouch (as used with or without cage 314) may also beattached at its proximal end to an alignment extension 316. Referring toFIG. 17C, alignment extension 316 is a tubular stent portion thatextends into the esophagus. In one embodiment, extension 316 may beapproximately 5 cm in length. It functions primarily to keep theproximal opening of the pouch aligned with the esophagus—so that foodpassing through the esophagus passes easily into the pouch.

Finally, an enclosed bypass tail (not shown) may extend from distalopening 308 of the pouch through the pylorus into the small bowel tosimulate a stomach bypass procedure. The structure of the tail may besimilar to the bowel tube described with respect to FIG. 5.

The stomach pouch and associated components may be implanted and removedusing procedures of the type described with respect to previousembodiments. In embodiments in which the stomach pouch includes thecage, alignment extension, and/or bypass tail, the components may beimplanted simultaneously as a single device. Alternatively, they may besegmented for separate implantation and for subsequent suture attachmentto one another once they are within the body.

Another embodiment of a satiation device is illustrated in FIG. 20. Thissatiation device includes a duodenal absorption barrier—an elongate tube400 that is positionable within the small intestine at a locationslightly distal of the ampulla of vader. For example, the barrier may bepositioned a distance of approximately 1 cm or more from the ampulla ofvader. Positioning of the tube so that it does not contact the ampulla(an opening through which bile passes into the duodenum) is desirable inthat it minimizes the chance of irritation and choleocystitus.

The tube 400 is preferably a flexible tube preferably approximately 20cm or more in length. It may be constructed as described with thesatiation devices described above. For example, it may be formed of aself-expandable material such as nitinol, stainless steel or a shapememory polymer (e.g. oligo-(caprolactone)-dimethacrylate or n-butylacrylate), and covered with a polymer covering that is resistant togastric juices (e.g. silicone) and that prevents passage of foodbyproducts through the walls of the tube.

The tube 400 prevents caloric intake in the small intestine bypreventing absorption of food through the walls of the duodenum, andthus functions as an aid to weight loss.

Tube 400 may be delivered and extracted using the techniques describedabove, and it may be held in place in any of the ways described herein,including sutures, barbs, scales, hooks, or under the outward pressureof the expanded device against the surrounding walls of the duodenum.Tube 400 may be used alone or in combination with components of the typedescribed above.

Various embodiments of satiation device have been described herein.These embodiments are giving by way of example and are not intended tolimit the scope of the present invention. It should be appreciated,moreover, that the various features of the embodiments that have beendescribed may be combined in various ways to produce numerous additionalembodiments.

It is claimed:
 1. A satiation pouch designed to be attached to apatient's stomach adjacent the gastro-esophageal junction therein, forlimiting the amount of food that can be consumed at one time, said pouchhaving walls that taper inwardly on progressing from a proximal openingto a smaller distal opening, the pouch being proportioned such that whenthe proximal opening is positioned at the distal end of a patient'sesophagus, the distal opening is disposed in the proximal region of thestomach, and said proximal and distal openings being proportioned suchthat food ingested by the patient can remain in the pouch until brokendown sufficiently for it to pass through the distal opening.
 2. Thepouch of claim 1 which is self-expanding to a saucer shape.
 3. The pouchof claim 1 which is self-expanding to an approximate funnel shape.